Highways and racetracks are often constructed with temporary or permanent barriers to contain and direct vehicles that have lost control. Conventionally the barriers are massive concrete walls which are either formed in place or are prefabricated in interlocking modules. The modules may be prefabricated in a concrete manufacturing facility and transported to the erection site to be lifted into place with cranes or forklift trucks.
An advantage of modular systems is that they can be used during highway construction to protect workers and equipment on a temporary basis, as well as in permanent installations. When the barriers are no longer required the modules may be reused in other locations. When a module is damaged it can be easily removed and replaced.
Typically conventional highway barrier modules include means to interconnect modules in a longitudinal series. One preferred conventional interconnecting means is a vertical tongue and groove however mechanical connections, such as bolts, are also used in permanent installations.
The size and weight of conventional barrier modules is such that they may be placed directly upon paved surfaces and do not require any anchoring to the surface in order to resist lateral impact loads from vehicles. The weight of the modules, interconnected with other like modules, provides inertial resistance and frictional resistance to sliding on their bases, thus preventing vehicles from crashing through the barriers into adjacent lanes of traffic or into highway ditches.
The use of concrete barrier modules is fairly widespread since they are durable and relatively inexpensive to construct. Abrasion between an impacting metallic vehicles creates sparks which often ignites the fuel of the vehicle which is spilled upon impact with the barrier. The danger of sparks is particularly significant due to the increased use of propane and natural gas as a fuel for vehicles. In the future it is also very likely that explosive hydrogen gas will be used to fuel significant numbers of vehicles.
A vehicle which looses control and crashes into a concrete barrier therefore may leak significant amounts of fuel. The vehicle may be abraded against the concrete barrier for an appreciable distance thereby creating sparks which may ignite the spilled fuel.
A further distinctive disadvantage of conventional concrete highway barriers is the rigidity of the concrete. An impacting vehicle often merely bounces off the rigid barrier and spins out of control into adjacent vehicles causing further accidents.
The concrete barrier does not yield and therefore the occupants of the impacting vehicle are protected from abrupt deceleration only by the collapsing action of their metal vehicle. Modern vehicles are often designed to absorb the impact of collision by folding up or collapsing the fenders or bumpers of the vehicle. The conventional concrete barrier does not aid in reducing the deceleration forces upon vehicle occupants.
To address the problems with rigid barriers, impact dispersing, or yielding non-rigid highway barriers are used on a widespread basis. Plastic barrels filled with sand are used to dissipate the deceleration forces upon impact around bridge abutments or other structures adjacent to highways. Sheet metal median barriers are also constructed which are filled with sand and deform under impact to dissipate the deceleration forces. W-shaped or closed box shaped sheet metal railings are also used supported on detachable pedestals.
Such impact dispersing or deformable barriers must be dissambled and rebuilt after an impact. Although the cost of maintaining such barriers is higher than a rigid concrete barrier, the deformable barriers often do not result in a vehicle merely bouncing off of the them into adjacent traffic. Deformable barriers are also often less expensive to initially construct.
Deformable rubber barriers have also been proposed with limited success. A common form of barrier is constructed of discarded automobile tires stacked or arranged in various configurations to absorb the impact of colliding vehicles. For example: U.S. Pat. No. 4,785,577 to Lederbauer; 4,066,244 to Yoho; and 3,951,384 to Hildreth Jr., all disclose various barriers constructed of complete discarded tire carcasses assembled into various configurations.
A distinct disadvantage of such conventional rubber barriers is that they are generally unsightly since they look like stacks of discarded automobile tires. The appearance of these barriers may not be a concern when used at a racetracks however for highway construction there suitability is minimal.
Waste tires present significant disposal problems. The waste tires are often stock piled in huge dumps which present a fire hazard.
Discarded automobile tires have been recycled successfully in various ways. Worn tires are ground or shredded and the rubber particles have been added to asphalt compositions, or have been bound together with polyurethane binders to create resilient pavements. One example of a resilient pavement is disclosed in U.S. Pat. No. 4,492,728 to Zurkinden. The resilient pavements are used to cover track and fields sports tracks and outdoor playground areas for example.
In such applications it is necessary that the binding and curing of the composition be carried on outdoors without special heating or humidity requirements.
A distinct disadvantage of using automobile tires in asphalt, or resilient pavement for sports facilities or playgrounds is that the metal wire reinforcement found in waste automobile tires must be first removed from the shredded rubber. The shredded rubber therefore must be ground to a fine particle size and passed over magnetic belts or other process machinery to remove the minute wire particles.
The additional cost and time taken to perform the metal removal adds to the cost of recycling the rubber and therefore reduces its desirability in suck applications.
A rubber barrier has been proposed in U.S. Pat. No. 5,106,554 to Drews which does not require the removal of wire from the recycled tires as follows. Tires are cut up into small squares and inserted within a mould in a wire cage. The cage is suspended away from the sides of the mould and the gap between the gap and the wire cage is filled with new rubber material. The barrier thus formed has solid new rubber envelope and an internal wire cage filled with pieces of discarded tire carcasses.
The Drews barrier suffers from several disadvantages. On severe impact, the barrier may become damaged, for example by ripping the exterior envelope from the central core. Due to the non-homogenous nature of the barrier, it is very likely that an impacting vehicle will merely rip off the outside skin of the barrier to reveal the interior wire cage and pieces of discarded tires therein. To repair the Drews barrier the moulding process must be carried out over again.
The Drews barrier also requires a wire cage to contain the recycled tire pieces during the moulding of the barrier. Added manufacturing steps and cost result from the construction of the cage, the filling of the cage (most likely done manually), and the insertion of the cage within the mould results in added costs and time taken to manufacture or re-manufacture the barriers.
The requirement of a cage also limits the shapes which a barrier may be formed using the Drews method. The requirement to include an internal cage however imposes a further restriction not only on the shape of the mould but also on a corresponding shape of cage required.
Prior conventional rubber barriers have also included wire cages or reinforcing to increase the resistance to the impacting vehicles. An example of a traffic control bumper guard rail is described in U.S. Pat. No. 3,317,189 to Rubenstein. A rubber and stone aggregate concrete composition is mixed in the process described in Rubenstein and the rubber concrete composition is encased within a wire reinforced envelope. Recycled rubber may be used in such an application however the use of a separate envelope and reinforcing wires add significantly to the cost of such a bumper.
The Rubenstein bumper suffers from the same disadvantage as the Drews barrier in that the bumper may be easily damaged on impact and must be removed and replaced. Due to the wire cage and complex construction of the bumper it is unlikely that salvaging the bumper material would be economical.
In the case of all prior art rubber barriers, integration of the rubber barrier into existing barrier structures is not contemplated. Instead, the rubber barriers of the prior art require that a separate structure be constructed, consuming additional space or removal of existing structures.
Therefore it is desirable to produce a rubber highway barrier which uses discarded waste tires preferably in a manner which does not require the removal of reinforcing steel from the discarded tires.
It is desirable that the content of new material used in such a barrier is minimized, to consume a maximum amount of recycled waste and to eliminate reinforcing structures which complicate fabrication, impede recycling efforts and add cost.
It is also desirable to produce a rubber barrier which may be itself recycled if damaged on impact with a vehicle.
It is also desirable to be able to form a rubber barrier in any selected shape. Preferably the rubber barrier should be easily integrated into existing concrete barrier modules, or assemblies of modules.